A diode comprises a PN junction formed by joining a block of P-type semiconductor with a block of N-type semiconductor. Multiple diodes are serially connected to form a diode string that facilitates integrated circuit (IC) device operation. The diode string provides a voltage drop in a circuit when the diode string is turned on in a forward bias condition, which can be used as a voltage adapter. With more advanced processes with smaller scales, there is a need for such a voltage adaptor to be operated with high supply voltage.